His father was Anthony O'Grady Lefroy, Colonial Treasurer of Western Australia for over 30 years.

On 2 August 1892, Lefroy was elected to the Western Australian Legislative Assembly seat of Moore in a by-election.

On 3 October 1911, Lefroy was again elected to the Legislative Assembly seat of Moore, after a hiatus of over ten years.

Wilson's government had difficulty maintaining parliamentary support, and was put under pressure to try to repeat the success at federal level of Prime Minister Billy Hughes in forming a Nationalist Party.

Lefroy's entire ministry was elected by the whole parliamentary party, and it remains the only non-Labor government of Western Australia to be chosen in this way.

When MacCallum Smith leaked this embarrassing information to the press, Lefroy resigned as premier and leader of the Nationalist Party on 17 April, and Hal Colebatch was elected in his place.